This invention relates to improved apparatus and methods for drilling holes laterally from a well bore.
In various well drilling situations, it may become desirable to first drill downwardly into the earth to a predetermined depth, and then at that depth drill one or more holes laterally from the main bore, either directly horizontally or at an inclination having a component transversely of the main well bore. For example, in a coal gasifying operation, a generally horizontal hole may extend between the lower ends of two vertical bores, to enable subjection of coal surrounding the horizontal hole to treatment in a manner converting the coal to a combustible natural gas.
Conventional directional drilling procedures are often inconvenient or ineffective for producing such a horizontal hole, since most conventional processes are incapable of changing the direction of a hole from vertical to horizontal as abruptly as might be desired. Instead, it is usually necessary to direct the drilling bit along a gradually curving path in changing to a horizontal condition. Further, the equipment required for conventional directional drilling may be relatively bulky, and expensive in both initial cost and operation and in other ways unsuited for use in recovering energy from coal.